Australian funnel-web spiders can cause lethal envenomation in humans due to the presence of potent δ-hexatoxins. The only available treatment is an antivenom comprising rabbit polyclonal antibodies. While functional, it suffers from batch-to-batch variability and can provoke adverse effects because of its non-human nature.
Spider toxins are notoriously difficult to obtain because of the limited amount of venom available from milking the spiders and the complexity of purification. Black widow spider latrodectins (Cys-rich peptides) have been successfully cloned and produced in the yeast Pichia pastoris. Latrodectins were folded correctly, including the formation of disulfide bonds, as we demonstrated by solving its soluble structure through NMR. Considering the common features between δ-hexatoxins and latrodectins (e.g., small peptide, rich in disulfide bonds produced by a spider), we are using the same expression strategy to produce δ-hexatoxins. Heterologous production allows for molecular redesign of the antigen, such as consensus toxins or toxins with special tags. Consensus toxins are artificially designed proteins representing an average sequence and, therefore, the intermediate structure of a curated selection of toxins. By using consensus toxins as targets in an antibody discovery campaign based on phage display technology, we aim to select antibodies that can broadly bind and neutralize the natural toxins used in the consensus design.
This novel discovery pipeline can be utilized to generate recombinant antivenom against δ-hexatoxins based on broadly-neutralizing human monoclonal antibodies. This may lead to safe and cost-effective therapeutics to treat funnel-web spider bite.